The charter of a big bank was up for renewal. A prominent US senator wrote to the bank's president to say he was under pressure to oppose the recharter, and it would be a good time for the bank to "refresh" his usual retainers.

It wasn't a subtle letter. Nor was this apparent quid pro quo (cash for a vote) condemned by Daniel Webster's Senate colleagues after his letter was exposed in 1833.

Today, such overt vote-buying is illegal. But politicians still ask corporations and organizations for money, so they can afford high-powered campaigns to win or keep their seats. And many donors still expect something in return for their contribution.

In the asking - and the giving - are a thousand shades of gray. But the huge sums of money trading hands in political contests have made politicians more vulnerable than ever to the appearance of corruption - if not actual bribery.

It's a development that many political observers say has soured the public - possibly even depressing voter turnout. Now, as the Senate takes up campaign-finance reform this week, the question is whether lawmakers will alter a campaign-finance system that they themselves thrive under.

"It's very rare that you see the kind of quid pro quo that constitutes bribery," says Charles Kolb, president of the Committee for Economic Development (CED), the first major business organization to recommend abolishing soft money. "The system is much more subtle than that. But even with the subtlety, the system doesn't look good."

Tracing the loophole

For most of the 20th century, corporate money was ruled out of federal elections. Union contributions have been banned since 1946. In 1968, both houses of Congress - prompted by Watergate and influence-peddling scandals - began to define standards of ethics for lawmakers and a system of peer review to enforce them.

But a 1979 revision of the campaign-finance law opened a loophole in the system that would later flood national campaigns with unregulated "soft" money, especially in the past decade. Critics say this new cash flow leaves Congress open to the charge that special interests are "buying" legislation - or that lawmakers are extorting big contributions.

"Every single special-interest group in America ... that through the use of money obtains access and influence in the legislative process is scared to death about this legislation because it diminishes their influence and power," said Sen. John McCain (R) of Arizona, cosponsor with Sen. Russell Feingold (D) of Wisconsin of a bill to abolish soft money.

Soft-money contributions soared in the last election cycle - jumping from $22 million in 1984 to more than $480 million last year. Instead of being limited to $1,000 contributions to a candidate, many people are now sending hundreds of thousands of dollars into politics under the soft-money label. And when such individuals and groups also have legislative interests at stake, it raises new ethical concerns.

"Watergate reforms were prompted by the shock that one donor had given more than $1 million to a campaign. In this last election cycle, more than 140 donors gave at least $1 million [each]," says Trevor Potter, co-chair of the Campaign Finance Institute.

The ostensible purpose of such soft-money contributions is to contribute to party-building activities. But legislative watchdogs such as the Washington-based Center for Responsive Politics often document a spike in corporate contributions around the time bills critical to their industry are before Congress.

For example, the credit-card industry widely expanded its contributions to candidates as it pushed an overhaul of bankruptcy legislation, which Congress passed last week.

"All this soft money raised by the campaign committees for the Senate and the House was being raised to impact the congressional elections," says Scott Harshbarger, president of Common Cause, a public advocacy group. "Now that the elections are over, the big soft-money givers are positioned to call in their chits."

Who's driving the money chase?

But business leaders say it's politicians who are driving the money chase. Nearly 1 in 3 business executives surveyed last year said that the No. 1 reason corporate America contributes to political campaigns is "to avoid adverse legislative consequences."

Experts say that the flood of unregulated money into politics is obscuring the line between ethical and unethical behavior. Lawmakers find themselves engaging in "something close to extortion when they go after those million-dollar contributions," says Thomas Mann, a fellow at the Washington-based Brookings Institution.

Democrats are testing that distinction in a civil lawsuit filed last year in the throes of the congressional campaign. Next month, a federal district court judge will take up a civil suit filed against House majority whip Tom Delay by the Democratic Congressional Campaign Committee. The suit charges that the Texas congressman threatened business groups with unfavorable legislative action if they did not increase their support of Republicans or decrease their support of Democrats. Republicans say they expect the charges to be dismissed.